1. Field of the Invention
The invention relates to the exchange of information among clients and servers in a computer network, such as the Internet. More particularly, this invention relates to a method and system for selecting a most suited server among multiple servers for responding to a client.
2. Description of the Related Technology
With the explosive use of computer networks, such as the Internet, internet service providers (ISPs) are struggling to keep up with an increased user demand for service. As used herein, the term ISP includes any individual, organization, or entity that provides access to and/or any service, such as electronic commerce transactions, over the Internet. The increase in user demand is mainly due to a heightened need to exchange frequent and large amounts of data, including various types of data such as electronic mail (E-mail), sound, image, video, and other data applications. As a result, ISPs are continuously challenged to provide a fast and efficient service while maintaining minimal server delay and breakdown.
Typically, the ISP places multiple mirrored servers (i.e., having substantially identical contents) in more than one location around the globe to maintain an acceptable level of service to users. It is up to the ISP to determine how to utilize and which of these mirrored servers will fulfill requests by a particular user. For example, one ISP may implement a round robin Domain Name Service (DNS) to distribute the load among these geographically dispersed servers. As the name implies, the term xe2x80x9cround robinxe2x80x9d refers to a method of selecting one of these servers at a time to fulfill a user requests in a cyclical or rotating fashion. However, the round robin method does not guarantee that users will experience an acceptable level of service. More particularly, the round robin method does not account for the server""s congestion or unavailability. The ISP may implement another method of selecting the geographically closest server as determined by client-to-server topological proximity. Such a method requires the implementing server to know the dynamically changing network topology, e.g., distances among and locations of servers, routers, etc. Moreover, just like the round robin method, the geographic method does not account for particular server availability, congestion, or downtime. The ISP may implement yet another method of redirecting user requests to the closest server as determined by a round-trip network latency. The term xe2x80x9clatencyxe2x80x9d refers to the amount of time a packet (i.e., a predefined set of data) takes to travel between a source and destination across the network. This method may be time-consuming because it involves the participation of distributed agent servers to measure roundtrip duration between the agents and the user. Additionally, this method necessitates reporting to the originating server the results of these measurements which consumes additional time. None of these methods offers a fast and efficient assessment of the best suited server to fulfill user requests.
Therefore, there is a need in the computer technology for a method and system for determining the most suitable server from multiple servers to fulfill user requests. The method and system should provide a substantially real-time assessment of server suitability without the necessity of special interoperability, or knowledge of network topology.
To overcome the above-mentioned limitations, the invention provides a method of selecting a host for a client in a client-server network. In one embodiment, the method comprises receiving a request to identify the host for the client. The method further comprises determining a future time at which a plurality of servers are to respond to the received request. The method further comprises sending a plurality of responses, each having an address representative of a respective host, from the plurality of servers at the future time. The method further comprises selecting the respective host address from the first arriving response of the plurality of responses. In another embodiment, the method comprises receiving a request to identify the host for the client. The method further comprises instructing each of a plurality of servers to respond to the received request, wherein the time of instructing is scheduled at a time that is related to the latency between each of the plurality of servers and an authoritative server. The method further comprises sending a plurality of responses, each having an address representative of a respective host, from the plurality of servers substantially immediately after receiving the instruction. The method further comprises selecting the respective host address from the first arriving response of the plurality of responses.
In another embodiment, the invention provides a system for selecting a host for a client. The system comprises a first server in communication within the client-server network, the first server being configured to determine a future time at which to respond to a local server. The system further comprises a second server in communication with the first server. The first server is further configured to instruct the second server to respond to the local server, and the second server is configured to send a response to the local server at substantially the same time as the response by the first server. The response to the local server includes an address representative of a respective host.